Search

Objective: To obtain active lipases for biodiesel production by refolding Proteus sp. lipase inclusion bodies expressed in E. coli., Results: A lipase gene lipPN1 was cloned from Proteus sp. NH 2-2 and expressed in E. coli BL21(DE3). Non-reducing SDS-PAGE revealed that recombinant LipPN1(rLipPN1) were prone to form inclusion bodies as disulfide-linked dimers in E. coli. Site-directed mutagenesis confirmed that Cys85 in LipPN1 was involved in the dimer formation. After optimizing the inclusion body refolding conditions, the maximum lipase activity reached 1662 U/L. The refolded rLipPN1 exhibited highest activity toward p-nitrophenyl butyrate at pH 9.0 and 40 °C. It could be activated by Ca 2+ with moderate tolerance to organic solvents. It could also convert soybean oil into biodiesel at a conversion ratio of 91.5%., Conclusion: Preventing the formation of disulfide bond could enhance the refolding efficiency of rLipPN1 inclusion bodies.

Experiments were carried out in six meat combines to establish the devitalization of Escherichia coli and bacteria of the Proteus genus at the thermal treatment of perishable meat products. Seventy series of experiments were conducted with 16 types of meat products of a different structure (homogenic and heterogenic), varying composition unequal diameter of the casings (3-4 am, 5-6 am, and 7-8 am), and different type of the latter--natural, paper, and cutis-lika. Twenty-four-hour agar cultures at a density of 10(5)-10(7) bacteria per gram of meat mass were used. In a series of experiments the temperature was dermined of the finished product when it reached 68 degrees C; in another group--after smoking and at various intervals during cooking; and in a third group of experiments the temperature was fillowed up during the entire thermal process, using thermo pairs. Studied was the heat resistance of the organisms tested under laboratory conditions, using the thermal curve in the production of meat products. The samples were investigated at the 24th, and 48th hour, and on the 5th day of room temperature storage. Results showed that devitalization of these organisms set in at 63 degrees C (E. coli) and 60 degrees (Proteus). The composition and homogeneity of the meat mass and the diameter of casings were found to have no effect on the heat resistance of these organisms.

Studied was the effect of the period of storing slaughtered broiler birds at low temperatures on the activity of pathogenic staphylococci, enteropathogenic Escherichia coli organisms and pathogenic species of the Proteus genus. It was found that freezing at minus 34 degrees C and storage of the slaughtered birds at minus 18 degrees C contribute to the considerable decrease in the bacterial count of the investigated test organisms, this being observed to a highest extent during the first fifteen days of storage.

Heat-labile enterotoxin (LT)-producing Escherichia coli and other enteric bacteria isolated from diarrheal Ethiopian children were studied for O and K antigen, production of heat-stable enterotoxin (ST), stability of LT production, properties of mannose-resistant hemagglutination (MRHA) (indicative of adhesive properties), and colonization factor antigen (CFA). Of the E. coli strains, 33% possessed O6, O8, or O78; 93% of these were stable producers of LT, and 86% produced both Lt and ST. O78 strains possessed CFA/I, whereas O6 and O8 strains possessed CFA/II. The E. coli with O antigens other than O6, O8, or O78, as well as the non-E. coli bacteria tended to lose their ability to produce LT; only 16% produced ST, and they only occasionally showed MRHA properties. The former group of E. coli strains might be considered as true enteropathogenic bacteria (enterovirulent E. coli), which may be identified serologically, while the pathogenic significance of the diversified latter group remains less certain.

An antigen common to Enterobacteriaceae and closely associated with endotoxin fractions has been separated by chromatography on DEAE cellulose employing elution with a NaCl gradient. The purified common antigen fails to coat erythrocytes, is poorly, if at all antigenic, it is non-dialyzable and excluded from sephadex G-100 gel. It is composed of polysaccharide and polypeptide. The most important property of this antigen thus far determined appears to be its interference with the specificity of the hemagglutination test commonly employed to measure antibody to O antigen of Enterobacteriaceae. It may also have taxonomic significance in classification of this family of bacteria.

Brock, Thomas D. (Indiana University, Bloomington), Barbara Peacher, and Deborah Pierson. A survey of the bacteriocines of enterococci. J. Bacteriol. 86:702-707. 1963.-A survey has been made of bacteriocine production by a wide variety of well-characterized strains of group D streptococci. On the basis of spectrums and sensitivity to chloroform, heat, and proteolytic enzymes, five distinct bacteriocines can be defined. Type 1 is produced by all Streptococcus zymogenes (S. faecalis var. zymogenes) strains, is active against a wide variety of gram-positive bacteria, and is also a hemolysin. Type 2 is produced by some S. liquefaciens (S. faecalis var. liquefaciens) strains, and acts on many enterococci as well as on certain other lactic acid bacteria. Type 3 is produced by certain strains of both S. faecalis and S. faecium, and inhibits a wide variety of group D streptococci, but is inactive against all other lactic acid bacteria tested except Leuconostoc citrovorum. Type 4 is produced by certain S. faecium strains and resembles in certain ways the type 3 activity, but differs from it in other ways. Type 5 has been found to be produced by only one proteolytic strain of S. zymogenes, and this bacteriocine has a very narrow spectrum. The strain that produces this bacteriocine also produces type 1 activity. No strain is sensitive to a bacteriocine of the type it produces.

A use-dilution procedure and screening method are proposed to aid the hospital bacteriologist in selecting the most effective disinfectants. Sixteen disinfectants were tested with and without organic material on six different organisms. Sporadic results usually obtained with quaternaries tested by the procedure of the Association of Official Agricultural Chemists (AOAC) were eliminated by the methods of this study. The use-dilution procedure employs the material upon which the disinfectant is to be used, rather than stainless steel, as in the AOAC use-dilution test. The importance of testing each disinfectant against several organisms and in the presence of organic material is discussed.

A new antibiotic was isolated from fermentations of Streptomyces erythreus designed for erythromycin A production. Isolation of this compound was accomplished by use of ion-exchange chromatography and countercurrent distribution. It crystallized from methyl isobutyl ketone in colorless acicular plates which melted at 127 to 130 C. The empirical formula was C(42)H(75)NO(14) with a molecular weight of 820. Electrometric titration in 66% dimethylformamide showed an apparent pKa of 8.4. Nuclear magnetic resonance, infrared, and ultraviolet absorption indicated a close resemblance of the compound to known erythromycins, although its chromatographic behavior and solubility differed from those of the known erythromycins. Its antimicrobial spectrum was similar to erythromycin A, but the minimal inhibitory concentrations were much higher.

Abel, K. (Melpar, Inc., Falls Church, Va.), H. deSchmertzing, and J. I. Peterson. Classification of microorganisms by analysis of chemical composition. I. Feasibility of utilizing gas chromatography. J. Bacteriol. 85:1039-1044. 1963.-The feasibility of utilizing gas chromatography as a sensitive and rapid method for the analysis of lipids as a natural basis for the classification of microorganisms by chemical composition was investigated. The lipids were extracted and transesterified to component carboxylic acid methyl esters in a single step, after which the methyl esters were resolved by gas chromatography to provide distinctive chromatographic elution patterns. Similarities in the lipid carboxylic acid distribution were noted among selected species of the family Enterobacteriaceae, and significant differences were noted among selected families of the class Schizomycetes.

Chang, Te-Wen (Tufts University School of Medicine, Boston, Mass.) and Louis Weinstein. In vitro biological activity of cephalothin. J. Bacteriol. 85:1022-1027. 1963.-Cephalothin is a "broad-spectrum" antibiotic active, in low concentrations, against Diplococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus. Shigella, Salmonella, and Proteus mirabilis were the most sensitive of the gram-negative organisms. Escherichia coli and Aerobacter aerogenes were suppressed to a lesser degree, whereas Pseudomonas aeruginosa and Herellea were highly resistant. Penicillin-sensitive and -resistant strains of S. aureus were equally susceptible to cephalothin. Exposure to increasing concentrations of the drug very frequently led to the development of resistance in gram-negative organisms; this was observed less often with S. aureus. Cephalothin stimulated the production of penicillinase by staphylococci, which remained sensitive to the cephalosporanic acid derivatives despite repeated subculture in increasing concentrations of the agent. Cephalothin was not inhibited by penicillinase. This antibiotic was more toxic to cultures of human amnion and mouse embryo cells than benzyl penicillin G but was less injurious than oxytetracycline, chlortetracycline, and demethylchlortetracycline; tetracylcine produced about the same degree of cellular damage as cephalothin.

Comparative tests in vitro for antibacterial activity were carried out with ampicillin, tetracycline, and chloramphenicol using 673 clinical isolates of Gram-negative bacilli and Streptococcus faecalis. Further comparative tests were also carried out with ampicillin, chloramphenicol, colistin sulphate, colistin methane sulphonate, cycloserine, kanamycin, nitrofurantoin, polymyxin, streptomycin, and tetracycline, using groups of 20 strains of each of the main species selected at random from the total number of isolates. Of the total number of isolates a higher percentage was inhibited by ampicillin than by tetracycline or chloramphenicol. Ampicillin showed particularly high activity against certain species of bacteria and displayed an antibacterial spectrum not shown by any of the other antibiotics tested.

The effect of xanthines on various microorganisms was studied. The antibacterial effect was not high; most of the test organisms could easily withstand a concentration of 2,500 mug/ml. Caffeine was more antibacterial than theophylline, and the latter more than theobromine. Caffeine citrate exhibited greater inhibitory effect than did pure caffeine. The effect was both bacteriostatic and bactericidal against susceptible organisms. The susceptibility of organisms to xanthines differed greatly even in related species. The morphology of Aerobacter aerogenes and A. cloacae was affected under the influence of caffeine; filamentation of cells followed sublethal doses. Potentiation was seen with antibiotics and caffeine; resistant strains were killed with a lower dose of drug in the presence of caffeine. This potentiating effect was pronounced with the tetracyclines; with streptomycin, the effect was the contrary.